Question

which statement about cholinergic synapses is correct? ach is pumped across the cleft; ach causes opening of na⁺ channels; ach breaks down ca²⁺; ach binds to presynaptic receptors

Explanation:

To determine the correct statement about cholinergic synapses:

• Option A: ACh (acetylcholine) diffuses across the synaptic cleft, not “pumped” (active transport). Eliminate A.
• Option B: ACh binds to postsynaptic receptors, causing ligand - gated Na⁺ channels to open (depolarization). This matches cholinergic synapse physiology.
• Option C: ACh is broken down by acetylcholinesterase, not “breaking down Ca²⁺”. Eliminate C.
• Option D: ACh binds to postsynaptic (not presynaptic) receptors. Eliminate D.

Answer:

B. ACh causes opening of Na⁺ channels